Recent advances in light emitting diode (LED) technology have produced products with much higher power and brightness, creating the need for effectively thermal management. Therefore, there is a growing interest in thermally conductive composite materials for the development of excellent heat dissipation materials. Thermal conducting polymer composites were produced utilizing UV-curable monomer mixtures and methacrylate-functionalized nanodiamond (ND). Although UV-radiation curing process in the presence of ND was found to limit to some extent on the synthesis of ND/polymer composites, the surface-modified ND showed more effectiveness in controlling mechanical properties of ND/polymer composites than non-modified ND, due to chemical grafting to polymer matrix. In addition, improved thermal conductivity of polymer composites was accomplished with the use of methacrylate-functionalized ND.